If you have been reading about Ac-SDKP and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
Several names appear in scientific and commercial contexts for this peptide. The label TB-500 is informal and does not follow standard biochemical nomenclature. Research articles more often describe the compound as a thymosin beta-4 fragment, Tβ4 fragment, or by its sequence Ac-LKKTETQ. Confusing TB-500 with full-length thymosin beta-4 can lead to incorrect assumptions about activity because the fragment lacks the remaining residues of the parent protein. The relationship between fragment and parent protein remains an active area of study.
Regulatory status differs by country, but TB-500 is not an approved pharmaceutical in major jurisdictions. It is commonly sold as a research chemical for laboratory use, which places responsibility for identity and purity on the supplier and the laboratory. Published human data are limited, and most reports involve preclinical models or cell culture. Questions about whether the fragment mimics all actions of thymosin beta-4, and under which conditions, remain open. Independent verification of any material is therefore a practical requirement in research settings.
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Calculated for the acetylated heptapeptide |
| Molecular weight | ~889 Da | Monoisotopic mass approximately 889.0 Da |
| Amino acid sequence | Ac-LKKTETQ | N-terminal acetylated seven-residue peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Water-soluble | Peptides of this size generally dissolve in aqueous media |
The most frequently cited identity is a seven-residue fragment with the sequence LKKTETQ, taken from the actin-binding domain of the parent protein. A separate molecule, N-acetyl-seryl-aspartyl-lysyl-proline, often shortened to Ac-SDKP, derives from the same protein's N-terminal region and appears in overlapping literature. Reported molecular masses therefore differ between sources, and a mass value on its own does not establish which fragment is present. Confirmation requires a defined sequence rather than a single number.
Research interest in thymosin beta-4 fragments centres on actin sequestration, cell migration and tissue repair models. Most published work uses cultured cells or animal wound and cardiac preparations, and findings are generally described as preliminary. No fragment of this protein has been approved as a therapeutic product by major regulators. Reviews of the field note inconsistent dosing, delivery routes and outcome measures across studies, which complicates direct comparison. The material is best understood as a laboratory reagent with an active but unresolved research literature.
No major regulatory agency has approved TB-500 for therapeutic use, and it holds no pharmacopoeial monograph. The name appears on the World Anti-Doping Agency prohibited list within the class covering peptide hormones, growth factors, and related substances. Detection in doping control relies on mass spectrometric methods applied to urine, often after preparation steps that concentrate the analyte. Discussion of TB-500 therefore clusters in biochemistry, sports medicine, and anti-doping literature rather than in registered clinical trials.
TB-500 is a synthetic peptide preparation marketed under a name derived from thymosin beta-4, a 43-residue actin-binding protein first isolated from thymus tissue. The full-length protein has a reported molecular mass near 4963 Da, while material sold as TB-500 is often described as a fragment containing the actin-binding motif LKKTETQ. Because suppliers use the name inconsistently, published sources sometimes refer to the same label as a fragment, a synthetic copy, or a related analog. This naming ambiguity complicates direct comparison of reports across studies.
Amidorphin is an endogenous, C-terminally amidated, opioid peptide generated as a cleavage product of proenkephalin A in some mammalian species; in humans and most other species, the peptide is 1 residue longer and is not amidated. Amidorphin is widely distributed in the mammalian brain, with particularly high concentrations found in the striatum, and outside of the brain in adrenal medulla and posterior pituitary. The 26-residue peptide named amidorphin is found in several species including bovine (Bos taurus), sheep (Ovis aries), and pig (Sus scrofa). Humans and commonly studied lab animals (mice, rats) produce a 27-residue peptide that does not have an amidated C-terminal residue; this is due to the absence of a Gly in the precursor sequence and replacement with Ala, which is not a substrate for the amidating enzyme (Peptidyl-glycine alpha-amidating monooxygenase). The properties of the 27-residue peptide are presumably similar to those of amidorphin, although this has not been adequately tested. In some brain areas, amidorphin is extensively further reduced into smaller fragments, such as the non-opioid peptide amidorphin-(8-26), or in humans, amidorphin-8-27. Cleavage of amidorphin into these smaller fragments releases the N-terminal [Met]-enkephalin sequence of amidorphin.
In 1911, he entered St Peter's College, Adelaide, where he excelled in chemistry, physics, mathematics and history. He played various sports for the school: cricket, Australian football, tennis, and track and field athletics as a sprinter and high jumper. The cost of his education was covered by four scholarships. He served in the Senior Cadets, in which he was commissioned as a second lieutenant in August 1916. After the First World War broke out in 1914, he wished to enlist, but parental permission was required and was not forthcoming. He was head boy in his final year at school, and was ranked twelfth in the state in his final examinations. Rather than become a businessman like his father, Florey elected to follow in the footsteps of his sister Hilda, who studied medicine. He entered the University of Adelaide in March 1917, his fees paid entirely by a state scholarship. This allowed him to continue his studies after his father died from a heart attack on 15 September 1918, and the shoe company was found to be insolvent and went into liquidation. Coreega and other properties had to be sold, and in 1920, the family moved into a bungalow in Glen Osmond. Florey participated in university athletics and tennis. He was an editor of the Medical Students' Society's Review and the Adelaide University Magazine. It was through the latter that he met Mary Ethel Hayter Reed, a fellow medical student, when he asked her to contribute an article on Women in Medicine.
=== Other inorganic compounds === Oxyhalides and oxysulfides of protactinium are known. PaOBr3 has a monoclinic structure composed of double-chain units where protactinium has coordination 7 and is arranged into pentagonal bipyramids. The chains are interconnected through oxygen and bromine atoms, and each oxygen atom is related to three protactinium atoms. PaOS is a light-yellow, non-volatile solid with a cubic crystal lattice isostructural to that of other actinide oxysulfides. It is obtained by reacting protactinium(V) chloride with a mixture of hydrogen sulfide and carbon disulfide at 900 °C. In hydrides and nitrides, protactinium has a low oxidation state of about +3. The hydride is obtained by direct action of hydrogen on the metal at 250 °C, and the nitride is a product of ammonia and protactinium tetrachloride or pentachloride. This bright yellow solid is thermally stable to 800 °C in vacuum. Protactinium carbide (PaC) is formed by the reduction of protactinium tetrafluoride with barium in a carbon crucible at a temperature of about 1400 °C. Protactinium forms borohydrides, which include Pa(BH4)4. It has an unusual polymeric structure with helical chains, where the protactinium atom has coordination number of 14 and is surrounded by six BH4− ions.
== Contraindications == Zopiclone causes impaired driving skills similar to those of benzodiazepines. Long-term users of hypnotic drugs for sleep disorders develop only partial tolerance to adverse effects on driving, with users of hypnotic drugs even after one year of use still showing an increased motor vehicle accident rate. Patients who drive motor vehicles should not take zopiclone as there is a significantly increased risk of accidents in zopiclone users. Zopiclone induces impairment of psychomotor function. Driving or operating machinery should be avoided after taking zopiclone as effects can carry over to the next day, including impaired hand-eye coordination. A double-blind study on the effect on performance of several hypnotic medications, relevant to military personnel who may have to be awakened to carry out duties, found that drugs listed in increasing order of performance impact duration were melatonin (with no impact), zaleplon, temazepam, and zopiclone. The effects on serial reaction time (SRT), logical reasoning (LRT), serial subtraction (SST), and multitask (MT) were measured. For zaleplon (10 mg), zopiclone (7.5 mg) and temazepam (15 mg) respectively the times to recover normal performance for SRT were 3.25, 6.25, and 5.25 hours; for LRT 3.25, >6.25, and 4.25 hours; for SST 2.25, >6.25, and 4.25 hours; and for MT 2.25, 4.25, and 3.25 hours. The study did not consider the effectiveness of the drugs on sleep.
Her writing has appeared in The Guardian, The Observer, the Times Literary Supplement, The Nation, Haaretz, Frieze Magazine, The Paris Review; former judge of the Jewish Quarterly-Wingate Prize. Lt. Col. Peter Lerner spokesperson to international media and commander of IDF social media activities; was born in London and attended Sinai School in Kenton, before his family moved to Israel; The Jewish Telegraphic Agency ranked him fifth among its most influential people on "Jewish Twitter", and Jewish News ranked him 18th on its "Aliyah 100" list of "those who have made a significant contribution to the State of Israel"; Director General of a new International Division of Israel's General Federation of Labour, the Histadrut. Lerner has written for Jerusalem Post, Jewish News, The Guardian, Haaretz. Bernard Levin (19 August 1928 – 7 August 2004) was an English journalist, author and broadcaster, described by The Times as "the most famous journalist of his day".
Sources: en.wikipedia.org
patient's age obesity presence of infection poor nutrition or hydration prescribed medication substance abuse and smoking general effect of the wound on a patient's lifestyle (pain, wound odor, excessive drainage)
Field and laboratory measurements have shown that reduced nitrogen-containing third-hand smoke compounds can partition from contaminated indoor surfaces into the gas phase and subsequently be taken up by aqueous aerosol particles, creating a particle-phase reservoir that allows THS components to persist and be redistributed within indoor air. Environmental tobacco smoke can oxidize with environmental nitrous acid to create carcinogenic (cancer-causing) tobacco-specific nitrosamines (TSNAs). One TSNA, called 4-(methylnitrosamino)-1-(3-pyridinyl)-1-butanone (also known as nicotine-derived nitrosamine ketone, or NNK), is a potent lung-specific carcinogen ubiquitous in tobacco smoke and smokers' homes, and has been detected on clothing fibers, dust, and in the air. Nitrosamines, along with other tobacco smoke chemicals that are deposited on surfaces or compounds that formed as a result of surface-phase reactions, can be a major source of toxicity, especially for infants. Infants can be particularly adversely affected given their frequent proximity to household surfaces and their propensity to ingest third-hand smoke residue from surfaces and dust. Review articles have suggested that third-hand smoke-type residues can arise not only from conventional tobacco smoking but also from emissions from e-cigarettes, cannabis and certain illicit substances, with the chemical composition, partitioning behaviour and routes of human exposure depending on the source material and indoor environment.
Director General Tim Davie acknowledges there are "grey areas" and says enforcing impartiality is a "difficult balancing act." Disgraced former pop star Gary Glitter is recalled to prison after breaching his licence conditions. Prime Minister Rishi Sunak announces an extra £5bn of government spending for UK defence over the coming two years. 14 March Royal Mail unveils its first design of a new set of ten special stamps, featuring garden flowers and a silhouette of King Charles III. Following a trial at Preston Crown Court, Eleanor Williams is sentenced to eight-and-a-half years in prison after falsely accusing several men of rape and claiming to have been trafficked by an Asian grooming gang. 15 March Chancellor of the Exchequer Jeremy Hunt presents the 2023 United Kingdom budget to the House of Commons, and says that the UK will avoid going into recession in 2023. The UK government commits to invest £20bn over the next 20 years in low-carbon energy projects, focusing on carbon capture and storage. Teachers, junior doctors, civil servants and Tube drivers stage a mass walkout, amid ongoing concerns regarding pay, jobs, pensions and working conditions. 16 March NHS staff in England, including nurses and ambulance staff, are offered a 5% pay rise from April along with a one-off payment of £1,655 to cover backdated pay. The offer does not include doctors, who are on a different contract.
== Prognosis == Prognosis depends on the condition itself. Some conditions such as MS depend on the subtype of the disease and various attributes of the patient such as age, sex, initial symptoms, and the degree of disability the patient experiences. Life expectancy in MS patients is 5 to 10 years lower than unaffected people. MS is an inflammatory demyelinating disease of the central nervous system (CNS) that develops in genetically susceptible individuals after exposure to unknown environmental trigger(s). The bases for MS are unknown but are strongly suspected to involve immune reactions against autoantigens, particularly myelin proteins. The most accepted hypothesis is that dialogue between T-cell receptors and myelin antigens leads to an immune attack on the myelin-oligodendrocyte complex. These interactions between active T cells and myelin antigens provoke a massive destructive inflammatory response and promote continuing proliferation of T and B cells and macrophage activation, which sustains secretion of inflammatory mediators. Other conditions such as central pontine myelinolysis have about a third of patients recover and the other two-thirds experience varying degrees of disability. In some cases, such as transverse myelitis, the patient can begin recovery as early as 2 to 12 weeks after the onset of the condition.
Sources: en.wikipedia.org
Systemic lupus erythematosus (SLE) Systemic sclerosis Polymyositis Dermatomyositis Rheumatoid arthritis (RA) Sjögren's syndrome Eosinophilic granulomatosis with polyangiitis (EGPA) Autoimmune thyroiditis Antiphospholipid antibody syndrome The treatment of overlapping connective tissue disorders is mainly based on the use of corticosteroids and immunosuppressants. Biologic drugs, i.e. anti-TNFα or anti-CD20 monoclonal antibodies, have been recently introduced as alternative treatments in refractory cases. There are some concerns with the use of anti-TNF agents in patients with systemic autoimmune diseases due to the risk of triggering disease exacerbations. The term polyangiitis overlap syndrome refers to a systemic vasculitis that shares features with two or more distinct vasculitis syndromes. The most common type of polyangiitis overlap syndrome is microscopic polyangiitis (MPA), which shares features with EGPA, granulomatosis with polyangiitis and panarteritis nodosa. Sometimes polyangiitis overlap syndrome is used as a synonym for MPA.
In a separate study of rehabilitative strength training following immobilization, creatine supplementation was associated with increased muscle MRF4 protein expression; however, whether changes in MRF4 directly mediate myonuclear accretion or hypertrophy remains uncertain.
=== April to June: Allied discussions === Balfour met Weizmann at the Foreign Office on 22 March 1917; two days later, Weizmann described the meeting as being "the first time I had a real business talk with him". Weizmann explained at the meeting that the Zionists had a preference for a British protectorate over Palestine, as opposed to an American, French or international arrangement; Balfour agreed, but warned that "there may be difficulties with France and Italy". The French position in regard to Palestine and the wider Syria region during the lead up to the Balfour Declaration was largely dictated by the terms of the Sykes–Picot Agreement and was complicated from 23 November 1915 by increasing French awareness of the British discussions with the Sherif of Mecca. Prior to 1917, the British had led the fighting on the southern border of the Ottoman Empire alone, given their neighbouring Egyptian colony and the French preoccupation with the fighting on the Western Front that was taking place on their own soil. Italy's participation in the war, which began following the April 1915 Treaty of London, did not include involvement in the Middle Eastern sphere until the April 1917 Agreement of Saint-Jean-de-Maurienne; at this conference, Lloyd George had raised the question of a British protectorate of Palestine and the idea "had been very coldly received" by the French and the Italians. In May and June 1917, the French and Italians sent detachments to support the British as they built their reinforcements in preparation for a renewed attack on Palestine.
Due to the high sulfur content of the Athabasca Oil Sands, stockpiles of elemental sulfur from this process exist throughout Alberta, Canada. Another way of storing sulfur is as a binder for concrete, the resulting product having some desirable properties (see sulfur concrete). The world production of sulfur in 2011 amounted to 69 million tonnes (Mt), with more than 15 countries contributing more than 1 Mt each. Countries producing more than 5 Mt are China (9.6), the United States (8.8), Canada (7.1) and Russia (7.1). Production has been slowly increasing from 1900 to 2010; the price was unstable in the 1980s and around 2010.
The Obama administration released a document compiled by U.S. investigators Dana Lesemann and Michael Jacobson, known as "File 17," which contains a list naming three dozen people, including the suspected Saudi intelligence officers attached to Saudi Arabia's embassy in Washington, D.C., which connects Saudi Arabia to the hijackers. Congress passed the Justice Against Sponsors of Terrorism Act. The practical effect of the legislation was to allow the continuation of a longstanding civil lawsuit brought by families of victims of the September 11 attacks against Saudi Arabia for its government's alleged role in the attacks. A U.S. judge formally allowed a suit to move forward against the government of Saudi Arabia brought by 9/11 survivors and victims' families. The families of some 9/11 victims obtained two videos and a notepad seized from Saudi national Omar al-Bayoumi by the British courts. The first video showed him hosting a party in San Diego for Nawaf al-Hazmi and Khalid al-Mihdhar, the first two hijackers to arrive in the U.S. The other video showed al-Bayoumi greeting the cleric Anwar al-Awlaki, who was blamed for radicalizing Americans and later killed in a CIA drone strike. The notepad depicted a hand-drawn airplane and some mathematical equations that, according to a pilot's court statement, might have been used to calculate the rate of descent to get to a target. According to a 2017 FBI memo, from the late 1990s until the 9/11 attack, al-Bayoumi was a paid cooptee of the Saudi General Intelligence Presidency.
Sources: en.wikipedia.org
TB-500 is a synthetic heptapeptide corresponding to a fragment of thymosin beta-4. It is used in laboratory research and is not an approved drug.
No. Thymosin beta-4 is a 43-amino-acid protein, while TB-500 represents only a short N-terminal segment. The two should not be treated as interchangeable in experimental design.
It is often called a thymosin beta-4 fragment, Tβ4 fragment, or Ac-LKKTETQ. The name TB-500 is mainly a commercial or catalog label rather than a formal chemical name.
No. Thymosin beta-4 is a 43-residue natural peptide, while TB-500 is a commercial label applied to a short synthetic fragment of it. The two differ in length, sequence coverage and how they are handled in the laboratory.